Our invention relates to a safety mechanism for an electrically powered machine, especially a hand-held power tool such as a drill or angle sander. It also relates to a stationary electrically powered machine such as a household appliance, which has a plug mechanism (e.g. according to DIN VDE 0625 Teil 1/11 87, Seiten 11, 12 und 59 or DIN German Society of Engineers 0625, Part 1, November 1987, pp. 11, 12 and 59) with a separate socket attached to a cord or power cable disconnectable from the appliance or machine and a plug built into the appliance.
Cords or cables are currently predominantly connected nonreleasably (i.e. the cord cannot be disconnected from the tool) with a power tool, although a hand-held power tool with the above-mentioned plug mechanism has a separable detachable power cord. This current structure has several disadvantages. The fixed attachment of the cord produces a bendable, slack part protruding from the outer surface of the appliance or hand-held power tool, which makes automatic manufacture particularly difficult. Among other things in different countries in which these machines are used different incompatible power grids are customary. This forces the manufacturer to market different machines according to the differences in the power grids in the different countries or to supply the machines without plugs and to place the responsibility of providing them on the customer.
Furthermore these nondisconnectable cables or power cords are prone to wear particularly in rough operating conditions; a worn-through or scraped cord attached nondisconnectably to the hand-held power tool can only be replaced by comparatively time-consuming methods.
One solution of this problem was to equip the machine with the above-mentioned separate cord with attached socket. This however results in a dangerous condition which might lead to injury: If the socket is again connected with the plug built into the unit, e.g. in an angle grinder, after a tool change and the switch of the power tool is in the "on" position, the angle grinder can tear the hand of the operator because of the starting moment. This situation can easily occur, because in tool changing the machine is disconnected by pulling the socket out and a switch inadvertently pressed in during tool changing is often not noticed.